Douglas K. Haines

Rapid alpha spectroscopy of evaporated liquid residues for emergency response.

A new method for &agr; spectroscopy of evaporated water residues was developed, consisting of evaporation of drinking water, flaming of the planchets, and &agr;-spectroscopic measurements using a grid ionization chamber. The method can identify and quantify radioactivity concentrations ≥3 mBq L−1 in a matter of several hours, whereas determination of sub-mBq L−1 levels is achievable in 1 day. Detailed investigations of flaming of the planchets, the humidity effect, and &agr; spectroscopy of thick sources are described. A three-dimensional calibration of the method was performed using standards containing 238U, 230Th, 239Pu, 241Am, and 244Cm radionuclides. In addition to its application to evaporated drinking water, this calibration is common for any environmental sample that can be prepared as a uniform layer, such as the residues from surface water, acidic washing or leaching from materials, as well as biological fluids such as urine. The developed method serves as a fast identifying or screening technique for emergency response involving &agr; radioactivity.

Emanation of radon from household granite.

Emanation of radon (222Rn) from granite used for countertops and mantels was measured with continuous and integrating radon monitors. Each of the 24 granite samples emitted a measurable amount of radon. Of the two analytical methods that utilized electret-based detectors, one measured the flux of radon from the granite surfaces, and the other one measured radon levels in a glass jar containing granite cores. Additional methods that were applied utilized alpha-scintillation cells and a continuous radon monitor. Measured radon flux from the granites ranged from 2 to 310 mBq m−2 s−1, with most granites emitting <20 mBq m−2 s−1. Emanation of radon from granites encapsulated in airtight containers produced equilibrium concentrations ranging from <0.01 to 11 Bq kg−1 when alpha-scintillation cells were used, and from <0.01 to 4.0 Bq kg−1 when the continuous radon monitor was used.

Non-destructive determination of 224Ra, 226Ra and 228Ra concentrations in drinking water by gamma spectroscopy.

Abstract— The U.S. Environmental Protection Agency mandates that drinking water showing gross alpha-activity greater than 0.19 Bq L−1 should be analyzed for radium, a known human carcinogen. The recommended testing methods are intricate and laborious. The method reported in this paper is a direct, non-destructive gamma-spectroscopic method for the determination of 224Ra, 226Ra, and 228Ra, the three radium isotopes of environmental concern in drinking water. Large-volume Marinelli beakers (4.1-L capacity), especially designed for measuring radioactive gases, in conjunction with a low-background, high-efficiency (131%) germanium detector were used in this work. It was first established that radon, the gaseous decay product of radium, and its progeny are quantitatively retained in this Marinelli beaker. The 224Ra, 226Ra, and 228Ra activity concentrations are determined from the equilibrium activities of their progeny: 212Pb, 214Pb (214Bi), and 228Ac; and the gamma-lines used in the analysis are 238.6, 351.9 (and 609.2), and 911.2 keV, respectively. The 224Ra activity is determined from the first 1,000-min measurement performed after expulsion of radon from the sample. The 226Ra activity is determined from the second, 2,400-min measurement, made 3 to 5 d later, and the 228Ra activity is determined from either the first or the second measurement, depending on its concentration level. The method’s minimum detectable activities are 0.017 Bq L−1, 0.020 Bq L−1, and 0.027 Bq L−1 for 224Ra, 226Ra, and 228Ra, respectively, when measured under radioactive equilibrium. These limits are well within the National Primary Drinking Water Regulations required limit of 0.037 Bq L−1 for 226Ra and for 228Ra. The precision and accuracy of the method, evaluated using the U.S. Environmental Protection Agency and the Environmental Resource Associates’ quality control samples, were found to be within acceptable limits.

Application of low-background gamma-ray spectrometry to monitor radioactivity in the environment and food

The results are described of an upgrade of the low-background gamma-ray spectrometry laboratory at New York State Department of Health by acquiring sensitivity to low-energy gamma rays. Tuning of the spectrometer and its low-energy response characteristics are described. The spectrometer has been applied to monitor the environment by measuring aerosols and water in New York State contaminated by the 2011 Fukushima accident plume. In addition, the spectrometer has been used to monitor radioactivity in food by performing a study of cesium in Florida milk.

Performance of a commercial radon-in-water measurement kit

Methods currently approved for the measurement of radon ((222)Rn) in water in New York State are liquid scintillation counting and emanation into alpha-scintillation cells. A passive system using an electret ion chamber (EIC) was evaluated as an alternative for the measurement of radon in water. Over 130 water samples from a community water supply containing 32BqL(-1) and 30 standards containing 686BqL(-1) were measured using the EIC method over 1- to 4-day exposure times. For comparison, identical samples were measured using liquid scintillation counting. Results of duplicate samples were typically within 5% for liquid scintillation counting and within 10% for the EIC. With respect to accuracy, the EIC produced results that were consistently low by 11-15%.

Rapid screening of radioactivity in food for emergency response

This paper describes the development of methods for the rapid screening of gross alpha (GA) and gross beta (GB) radioactivity in liquid foods, specifically, Tang drink mix, apple juice, and milk, as well as screening of GA, GB, and gamma radioactivity from surface deposition on apples. Detailed procedures were developed for spiking of matrices with (241)Am (alpha radioactivity), (90)Sr/(90)Y (beta radioactivity), and (60)Co, (137)Cs, and (241)Am (gamma radioactivity). Matrix stability studies were performed for 43 days after spiking. The method for liquid foods is based upon rapid digestion, evaporation, and flaming, followed by gas proportional (GP) counting. For the apple matrix, surface radioactivity was acid-leached, followed by GP counting and/or gamma spectrometry. The average leaching recoveries from four different apple brands were between 63% and 96%, and have been interpreted on the basis of ion transport through the apple cuticle. The minimum detectable concentrations (MDCs) were calculated from either the background or method-blank (MB) measurements. They were found to satisfy the required U.S. FDAs Derived Intervention Levels (DILs) in all but one case. The newly developed methods can perform radioactivity screening in foods within a few hours and have the potential to capacity with further automation. They are especially applicable to emergency response following accidental or intentional contamination of food with radioactivity.

Multifarious application of well-type germanium detector

A low-background well-type high-purity germanium detector system, with high counting efficiencies for X-rays and low-energy g-rays, was used to determine several radionuclides of environmental, biomedical, or geological interest. These included 125I, 129I, 210Pb, 226Ra, 234Th (daughter of 238U), 239Pu, 240Pu and 241Am. Methods were devized for their determinations in diverse environmental matrices or under laboratory procedural conditions. Counting efficiencies and minimum detectable activities for each nuclide were determined under the experimental conditions. These methods are being applied to our service analysis.

Radon measurement of natural gas using alpha scintillation cells

Due to their sensitivity and ease of use, alpha-scintillation cells are being increasingly utilized for measurements of radon ((222)Rn) in natural gas. Laboratory studies showed an average increase of 7.3% in the measurement efficiency of alpha-scintillation cells when filled with less-dense natural gas rather than regular air. A theoretical calculation comparing the atomic weight and density of air to that of natural gas suggests a 6-7% increase in the detection efficiency when measuring radon in the cells. A correction is also applicable when the sampling location and measurement laboratory are at different elevations. These corrections to the measurement efficiency need to be considered in order to derive accurate concentrations of radon in natural gas.